From basic mechanics it is well known that a force is the action of one body on another body. In many circumstances, just how generated forces alter or affect a body can be of great concern. Most certainly, this concern is present whenever machines are designed which have moving parts. Further, the concern is present whenever machines are used to assemble component parts into an end product.
With the above in mind, it is helpful to review some basic mechanical concepts. According to Newton's first law, if the resultant force acting on a body is zero, the body will remain at rest (static condition) or move in a straight line with a constant velocity (dynamic condition). According to Newton's second law, if the resultant force acting on a body is not zero, the body will have an acceleration which is proportional to the magnitude of the resultant and in the direction of this resultant force. Stated differently, F=ma, where F represents a resultant force vector acting on the body, m is the mass of the body, and a is the acceleration vector of the body. As will be more fully appreciated in the discussion which follows, the present invention relies on notions inherent in the mechanical concepts set forth above for the control of moving parts in an assembly and manufacturing machine. When considering the operation of a machine that is to be used for the purpose of either assembling separate individual component parts into an end product, or moving a tool into contact with a work surface of the end product, the consequences of the manufacturing process on the end product must be addressed. For example, consider a machine used for the manufacture of an end product which incorporates a probe assembly that is to be moved, for whatever purpose, into contact with a work surface on the end product. Since the machine will necessarily operate to move one body (the probe assembly) into contact with another body (the work surface of the end product), forces will be generated against both bodies by this action. It happens, however, that many end products incorporate very delicate and fragile components which could be easily damaged if the contact forces that are generated during assembly of the end product become too great. Consequently, in order to avoid damage to the end product, it is often desirable that only very small magnitude forces be generated against specified component parts of the end product during its assembly or manufacture.
The present invention recognizes that by monitoring certain measurable values of the movement parameters of a particular machine part, the contact forces between the machine part and components of the end product being manufactured can be accurately controlled and thereby minimized. Stated differently, based on the basic mechanical concepts set forth above, the present invention recognizes that the measurable values of the movement parameters of the machine part which can be monitored to control the machine part are all force related.
In light of the above, it is an object of the present invention to provide a method and a device for moving a probe assembly into soft contact with a work surface which selectively monitors specified movement parameters of the probe assembly to ensure soft contact between the probe assembly and the work surface. It is another object of the present invention to provide a method and device for moving a probe assembly into soft contact with a work surface which relies on selective modes of operation that respectively require position control, or velocity control, or torque control with acceleration information of the probe assembly to ensure soft contact between the probe assembly and the work surface. Still another object of the present invention is to provide a method and device for moving a probe assembly into soft contact with a work surface which prevents damage to the work surface. Yet another object of the present invention is to provide a method and device for moving a probe assembly into soft contact with a work surface that will provide precision measurements of the work surface or in relation to the work surface. Still another object of the present invention is to provide a method for moving a probe assembly into soft contact with a work surface which is easy to execute and comparatively cost effective.